ALLEGHENY FORMATION EAST OP ALLEGHENIES 77 



The Kelly coal bed, clearly equivalent to the Upper Freeport, disap- 

 pears in the northern part of the field, but increases southward and be- 

 comes of great commercial importance in Bedford county, though even 

 there it varies in thickness from 4 inches to 16 feet in one mine. It is 

 usually double, and the parting has been found 1 inch to 10 feet on a 

 single property. The upper division is ordinarily single, but the lower 

 is often divided into several benches. The interval to the Twin coal bed 

 is occupied at times wholly by shale, but on the western side of the field 

 it contains a coarse sandstone which may be taken as representing both 

 the Butler and the Freeport sandstone, as the Lower Freeport coal bed is 

 not here. The interval in Huntingdon county varies from 90 to 110 feet, 

 but in Bedford from 65 to 118, being greatest on the westerly side, where 

 the sandstones are most prominent. The Twin coal bed is persistent 

 throughout the field and derives its name from the fact that at times it 

 and the Barnett below are almost in contact, so that they may be mined 

 as one bed. In Bedford county the coal varies from worthless to good 

 and in thickness from 1 to 6 feet, so that it is unimportant ; but in Hunt- 

 ingdon its coal is good, and when near enough to the Barnett is mined. 

 The interval to the Barnett varies from 6 inches to 30 feet, though rarely 

 less than 2 feet. Within 200 rods, on Sixmile creek, in Bedford, the 

 thickness was measured, 37, 19, and 7 feet. The thinning is toward the 

 east, but not regularly so. In Huntingdon, Doctor White found it 

 8, to 30 feet on one property, but on another, in the eastern part of the 

 field, the variation is from 6 inches to 7 feet. The Barnett coal bed 

 always carries bony coal, 3 to 10 inches thick on top, and in the main 

 coal usually shows two benches separated by a variable parting. At one 

 mine Doctor White made this measurement : - • 



Feet. Inches 



1. Twin coal bed 2 



2. Shale and rock 4 



3. Barnett coal bed 17 9 



Feet. Inches 



Bony coal 9 



Coal 2 6 



Shale 3 



Sandstone 11 



Coal 6 



This parting of 14 feet soon disappears, and in another part of the mine 

 the bottom coal is in contact with the upper. The variability of this part- 

 ing is a familiar phenomenon, as the mining operations on this bed are 

 extensive within Huntingdon county. Doctor White correlates this bed 

 with the Lower Kittanning of Blair county, to which it bears close resem- 



